Color filter

ABSTRACT

A color filter that is adapted to be changeably used for a twisted nematic (TN) mode LCD and a in plane switching mode (IPS) mode LCD by forming a light-shielding layer at the rear side of a transparent substrate to improve a surface morphology. In the color filter, a light-shielding layer is formed from a metal material on a second surface of a transparent substrate having first and second surfaces to have a lattice shape. First, second and third filters are formed at a portion which does not correspond to the light-shielding layer on the first surface of the transparent substrate in such a manner to has a desired portion overlapped with the light-shielding layer, thereby transmitting red, green and blue color lights, respectively. Accordingly, the light-shielding layer is formed on the second surface of the transparent substrate to prevent a deterioration of surface morphology. Even though the first and second light-shielding layers are removed by stripped particles generated during the continuous deposition process to provide the pinholes, a light leakage can prevented by virtue of the third light-shielding layer. Also, the first to third light-shielding layers are made from a metal or a metal oxide, so that it becomes possible to prevent a generation of stain badness caused by an adhesion weakness between the light-shielding layer and the transparent substrate.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] This invention relates to a color filter for a liquid crystaldisplay (LCD), and more particularly to a color filter that is adaptedto be changeably used for a twisted nematic (TN) mode LCD and a in planeswitching mode (IPS) mode LCD by forming a light-shielding layer at therear side of a transparent substrate to improve a surface morphology.

[0003] 2. Description of the Related Art

[0004] Generally, a liquid crystal display (LCD) includes switchingdevices constituted by thin film transistors each of which consists of agate electrode, a gate insulating film, an active layer, an ohmiccontact layer, source and drain electrode, and a liquid crystal injectedbetween a lower plate provided with pixel electrodes and an upper plateprovided with color filters. The color filter includes red(R), green(G)and blue(B) unit filters on a transparent substrate, and alight-shielding layer for preventing a deterioration of brightness andcolor purity among these unit filters. The color filter has a differentconfiguration depending on a mode of the LCD. In the color filter usedfor the TN mode, a common electrode is formed on the unit filters. Onthe other hand, in the color filter used for the IPS mode, a protectivefilm, instead of the common electrode, is formed on the unit filters andthe light-shielding layer is made from only a resin so as to prevent aundesired affect to a horizontal electric field of the lower plate.Also, in the color filter used for the IPS mode, a transparent groundelectrode for eliminating a static electricity at a screen is formed atthe rear surface of the transparent substrate, that is, at the surfacein which the unit filters are not formed.

[0005]FIG. 1 is a section view showing a structure example of aconventional color filter for a TN mode LCD. Referring to FIG. 1, in theconventional color filter, a first light-shielding layer 13 formed of ametal oxide film and a second light-shielding layer 15 formed of a metalfilm are disposed in a lattice shape on a transparent substrate 11. Thefirst light-shielding layer 13 may be formed of a twofold filmconsisting of a metal oxide film and a metal nitride film. First, secondand third filters 17 a, 17 b and 17 c for transmitting R, G and B colorlights, respectively are formed at a portion in which the first andsecond light-shielding layers 13 and 15 on the transparent substrate 11are not formed. The first, second and third filters 17 a, 17 b and 17 cis made from an acrylic resin or polyimide group resin dispersed withpigments, and is separately formed on the first and secondlight-shielding layers 13 and 15 so as to prevent a color mixture.

[0006] A common electrode 19 made from a transparent conductive materialsuch as an indium tin oxide (ITO), a tin oxide (TO) or an indium zincoxide (IZO), etc. is formed on the first to third filters 17 a, 17 b and17 c. The common electrode 19 allows the first to third filters 17 a, 17b and 17 c to be not contacted with a liquid crystal so as to preventits damage.

[0007]FIG. 2 is a section view showing a structure example of aconventional color filter for an IPS mode LCD. Referring to FIG. 2, inthe conventional color filter, a light-shielding layer 23 in which aresin dispersed with an electrically insulated black pigment has alattice shape is formed on a transparent substrate 21. First, second andthird filters 27 a, 27 b and 27 c for transmitting R, G and B colorlights, respectively are formed at a portion in which thelight-shielding layer 23 are not formed. The first, second and thirdfilters 27 a, 27 b and 27 c are made from an acrylic resin or polyimidegroup resin dispersed with pigments, and is separately formed on thelight-shielding layer 23 so as to prevent a color mixture. In the caseof forming the light-shielding layer 23 from a conductive material, ahorizontal electric field generated from the lower plate causes drivebadness by a noise upon drive control due to a derived electric fieldgenerated by the conductive material.

[0008] A protective layer 25 is formed on the first to third filters 27a, 27 b and 27 c. The protective layer 25 plays a role to prevent thefirst to third filters 27 a, 27 b and 27 c from being contacted with aliquid crystal to cause its damage, and is made from a transparentmaterial having a insulation characteristic such as polyimide. A groundelectrode 29 is formed on the rear surface of the transparent substrate21, that is, on the surface in which the first to third filters 27 a, 27b and 27 c. The ground electrode 29 eliminates a static electricity on ascreen to prevent a generation of domain stains, and is made from atransparent conductive material such as ITO, TO or IZO, etc.

[0009] However, the conventional color filter has a problem in that astep difference is generated at a portion where each of the filtersoverlaps by a thickness of the light-shielding layer to deteriorate asurface morphology. Meanwhile, the TN mode color filter has a problem inthat, when a stacked structure of a metal oxide film and a metal film isformed, pinholes are generated during the cleaning after a generation ofstripped particles in a continuous film formation process to cause alight leakage phenomenon. The IPS mode color filter has a problem inthat, since the light-shielding layer is made from only a resin andformed after formation of the ground electrode, a stain is generated dueto its contact with a conveyer machine (e.g., a roller and a robot hand,etc.) upon formation of the ground electrode at the rear side of thetransparent substrate, or an adhesion between the light-shielding layerand the transparent substrate is weakened to generate stain badness.

SUMMARY OF THE INVENTION

[0010] Accordingly, it is an object of the present invention to providea color filter wherein a light-shielding layer is formed at the rearside of a transparent substrate to prevent a deterioration of surfacemorphology.

[0011] A further object of the present invention is to provide a colorfilter that is capable of preventing a light leakage caused by pinholesgenerated at a light-shielding layer.

[0012] A yet further object of the present invention is to provide acolor filter that is capable of preventing stain badness caused by anadhesion weakness between a light-shielding layer and a transparentsubstrate.

[0013] In order to achieve these and other objects of the invention, acolor filter according to an embodiment of the present inventionincludes a light-shielding layer formed from a metal material on asecond surface of a transparent substrate having first and secondsurfaces to have a lattice shape; and first, second and third filters,being formed at a portion which does not correspond to thelight-shielding layer on the first surface of the transparent substratein such a manner to has a desired portion overlapped with thelight-shielding layer, to transmit red, green and blue color lights,respectively.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] These and other objects of the invention will be apparent fromthe following detailed description of the embodiments of the presentinvention with reference to the accompanying drawings, in which:

[0015]FIG. 1 is a section view showing a structure example of aconventional color filter for a TN mode LCD;

[0016]FIG. 2 is a section view showing a structure example of aconventional color filter for an IPS mode LCD;

[0017]FIG. 3 is a section view showing a structure of a color filter fora TN mode LCD according to an embodiment of the present invention;

[0018]FIG. 4 is a section view showing a structure of a color filter fora IPS mode LCD according to another embodiment of the present invention;and

[0019]FIG. 5A to FIG. 5D represents a process of fabricating a colorfilter shown in FIG. 3.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0020] Referring to FIG. 3, there is shown a color filter for a TN modeLCD according to an embodiment of the present invention. In the colorfilter, first and second light-shielding layers 33 and 35 are disposedin a lattice shape on a second surface of a transparent substrate 31having first and second surfaces. The first light-shielding layer 33 ismade from a metal such as chrome (Cr) to have a thickness of more than800Å while the second light-shielding layer 35 is made from a metaloxide such as chrome oxide (Cr₂O₃) to have a thickness of 300 to 1000Å.Alternatively, the first and second light-shielding layers 33 and 35 maybe formed of a twofold film consisting of a metal oxide film and a metalnitride film. An incident light is reflected from each surface of thefirst and second light-shielding layers 33 and 35. Each light reflectedfrom the surfaces of the first and second light-shielding layers 33 and35 undergoes an extinction interference to prevent a progress of thelight.

[0021] A third light-shielding layer 37 is formed in a lattice shape onthe first surface opposed to the second surface provided with the firstand second light-shielding layers 33 and 35 of the transparent substrate31. The third light-shielding layer 37 is formed from a metal oxide filmsuch as chrome oxide (Cr₂O₃) to have a thickness of 300 to 700Å at aportion opposite to the first and second light-shielding layers 33 and35. Thus, the third light-shielding layer 37 can prevent a generation oflight leakage even though the first and second light-shielding layers 33and 35 are removed by stripped particles to provide pinholes.

[0022] The first to third filters 39 a, 39 b and 39 c for transmittingR, G and B color lights, respectively are formed at a portion where thethird light-shielding layer 37 on the first surface of the transparentsubstrate 31 is not formed. The first to third filters 39 a, 39 b and 39c are made from an acrylic or polyimide group resin dispersed with R, Gand B pigments and are separately formed on the third light-shieldinglayer 37 so as to prevent a color mixture. Since the thirdlight-shielding layer 37 is formed into a small thickness, the first tothird filters 39 a, 39 b and 39 c has a reduced step difference at aportion overlapping with the third light-shielding layer 37 to improve asurface morphology.

[0023] A common electrode 41 made from a transparent conductive materialsuch as ITO, TO or IZO is formed on the first to third filters 39 a, 39b and 39 c. The common electrode 41 drives a liquid crystal with avoltage difference from a pixel electrode at a lower plate (not shown).Also, the common electrode 41 prevents the first to third filters 39 a,39 b and 39 c from being contacted with the liquid crystal to causetheir damage.

[0024] Referring to FIG. 4, there is shown a color filter for an IPSmode LCD according to another embodiment of the present invention. Thecolor filter for the IPS mode LCD has a structure similar to the colorfilter for the TN mode LCD shown in FIG. 3 except that a protectivelayer 61 instead of the common electrode 41 is formed on the first tothird filters 39 a, 39 b and 39 c. More specifically, first and secondlight-shielding layers 53 and 55 are disposed in a lattice shape on asecond surface of a transparent substrate 51. A third light-shieldinglayer 57 is formed on the first surface opposed to the second surface ata portion corresponding to the first and second light-shielding layers53 and 55. The first to third filters 59 a, 59 b and 59 c fortransmitting R, G and B color lights, respectively are formed at aportion where the third light-shielding layer 57 on the second surfaceare not provided.

[0025] A protective layer 61 made from a transparent insulation materialsuch as an epoxy resin or an acryl, etc. is formed on the first to thirdfilters 59 a, 59 b and 59 c. The protective layer 61 prevents the firstto third filters 59 a, 59 b and 59 c from being contacted with a liquidcrystal and thus prevents their damage.

[0026] In the above-mentioned structure, a conductive material layerdoes not exist on the first surface of the transparent substrate 51, sothat it can be prevented to make an undesired affect to a horizontalelectric field of a lower plate (not shown). The first light-shieldinglayer 53 formed from a metal such as a chrome(Cr) on the second surfaceof the transparent substrate 51 may be used as a ground electrode foreliminating a static electricity on a screen. Also, the firstlight-shielding layer 53 is made from a metal while the second and thirdlight-shielding layers 55 and 57 being made from a metal oxide, anadhesive force to the transparent substrate 51 is improved to prevent ageneration of stain badness.

[0027]FIG. 5A to FIG. 5B represent a process of fabricating the colorfilter shown in FIG. 3. Referring to FIG. 5A, the first and secondlight-shielding layers 33 and 35 having a lattice shape are formed onthe second surface of the transparent substrate 31 having the first andsecond surfaces. The first and second light-shielding layers 33 and 35is formed by continuously depositing a metal oxide film such as atwofold film of a metal and a chrome oxide (Cr₂O₃) or a metal nitridefilm such as a twofold film of a chrome oxide (Cr₂O₃) and a chromenitride (CrN_(y)O_(x)) on the second surface of the transparentsubstrate 31 into a thickness of about 1000 to 2000Å and a thickness ofabout 300 to 700Å using the sputtering technique and then patterning thesame using the photolithography.

[0028] Referring to FIG. 5B, the third light-shielding layer 37corresponding to the first and second light-shielding layers 33 and 35is formed on the first surface of the transparent substrate 31. Thethird light-shielding layer 37 is formed by depositing a metal oxidefilm such as chrome oxide (Cr₂O₃) on the first surface of thetransparent substrate 31 into a thickness of about 300 to 700Å using thesputtering technique and then patterning the same using thephotolithography. At this time, the third light-shielding layer 37 ispatterned to correspond to the first and second light-shielding layers33 and 35. The third light-shielding layer 37 prevents a generation oflight leakage even though the first and second light-shielding layers 33and 35 formed on the second surface of the substrate 31 are removed bystripped particles to provide pinholes.

[0029] Referring to FIG. 5C, the first filter 39A for transmitting onlyany one of R, G and B color lights, for example, only the R color lightis provided at a desired portion on the first surface of the transparentsubstrate 31. The first filter 39 a is formed by coating an acrylic orpolyimide group resin dispersed with a R color pigment on the firstsurface of the transparent substrate 31 and then exposing and developingthe same and thereafter patterning the same in such a manner to be leftonly at a desired portion thereof. At this time, the first filter 39 aoverlaps with the desired portion of the third light-shielding layer 37.Since the third light-shielding layer 37 has a small thickness, thefirst filter 39 a has a reduced step difference at a portion overlappingwith the third light-shielding layer 37 to thereby improve a surfacemorphology in comparison to the case of forming the existent blackmatrix film of a metal or a resin.

[0030] Referring to FIG. 5D, the second and third filters 39 b and 39 care continuously formed at a desired portion on the first surface of thetransparent substrate 31 in the same manner as the first filter 39 a.The second and third filters 39 b and 39 c transmit only G and B colorlights except for an R color light in the R, G and B color lights. Atthis time, since the third light-shielding layer 37 has a smallthickness, the second and third filters 39 b and 39 c also have areduced step difference at a portion overlapping with the thirdlight-shielding layer 37 to improve a surface morphology.

[0031] The transparent common electrode 41 is formed on the first tothird filters 39 a, 39 b and 39 c. The common electrode 41 is formed bydepositing a transparent conductive material such as ITO, TO or IZO,etc. on the first to third filters 39 a, 39 b and 39 c using thesputtering technique.

[0032] To form the first and second light-shielding layers 53 and 55having a lattice shape on the second surface of the transparentsubstrate 51 and then the third light-shielding layer 57 on the firstsurface and thereafter form the first to third filters 59 a, 59 b and 59c on the first surface of the transparent substrate 51 in a method offabricating the color filter shown in FIG. 4 is similar to that in themethod of fabricating the color filter shown in FIG. 3.

[0033] In the method of fabricating the color filter shown in FIG. 4,however, the protective layer 61 is formed from a transparent insulationmaterial such as an epoxy resin or an acryl, etc. on the first to thirdfilters 59 a, 59 b and 59 c unlike the method of fabricating the colorfilter shown in FIG. 3. According to the method of fabricating the colorfilter shown in FIG. 4, the first light-shielding layer 53 is made froma metal while the second and third light-shielding layers 55 and 57being made from a metal oxide, so that an adhesive force to thetransparent substrate 51 can be improved to prevent a generation ofstain badness.

[0034] As described above, according to the present invention, thelight-shielding layer is formed on the second surface of the transparentsubstrate to prevent a deterioration of surface morphology. Also, eventhough the first and second light-shielding layers are removed bystripped particles generated during the continuous deposition process toprovide the pinholes, a light leakage can prevented by virtue of thethird light-shielding layer. In addition, the first to thirdlight-shielding layers are made from a metal or a metal oxide, so thatit becomes possible to prevent a generation of stain badness caused byan adhesion weakness between the light-shielding layer and thetransparent substrate.

[0035] Although the present invention has been explained by theembodiments shown in the drawings described above, it should beunderstood to the ordinary skilled person in the art that the inventionis not limited to the embodiments, but rather that various changes ormodifications thereof are possible without departing from the spirit ofthe invention. Accordingly, the scope of the invention shall bedetermined only by the appended claims and their equivalents.

What is claimed is:
 1. A color filter comprising: a light-shieldinglayer formed from a metal material on a second surface of a transparentsubstrate having first and second surfaces to have a lattice shape; andfirst, second and third filters, being formed at a portion which doesnot correspond to the light-shielding layer on the first surface of thetransparent substrate in such a manner to has a desired portionoverlapped with the light-shielding layer, to transmit red, green andblue color lights, respectively.
 2. The color filter according to claim1 , wherein the light-shielding layer is a stacked structure of a firstlight shielding layer formed from a metal film and a secondlight-shielding layer formed from a metal oxide film or a metal nitridefilm.
 3. The color filter according to claim 2 , wherein the firstlight-shielding layer is made from a chrome (Cr) to have a thickness ofmore than 800 Å.
 4. The color filter according to claim 2 , wherein thesecond light-shielding layer is formed of a twofold film of a chromeoxide (Cr₂n₃) and a chrome nitride (CrN_(y)O_(x)) to have a thickness of300 to 1000 Å.
 5. The color filter according to claim 2 , furthercomprising: a third light-shielding layer formed from a metal materialat a portion corresponding to the light-shielding layer on the firstsurface of the transparent substrate to have a lattice shape.
 6. Thecolor filter according to claim 5 , wherein the third light-shieldinglayer is made from a chrome oxide (Cr₂O₃) to have a thickness of 300 to1000Å.
 7. The color filter according to claim 1 , wherein the first,second and third filters are separately formed from an acrylic orpolyimide group resin dispersed with pigments.
 8. The color filteraccording to claim 1 , further comprising: a transparent commonelectrode formed from an indium thin oxide (ITO), a tin oxide (TO) or anindium zinc oxide (IZO) on the first, second and third filters.
 9. Thecolor filter according to claim 1 , further comprising: a protectivelayer formed from a transparent insulation material of an epoxy resin oran acryl on the first, second and third filters.